In the field of information processing, virtualization technology is used which allows a plurality of virtual computers (which may also be referred to as virtual machines or logic hosts) to operate on a physical computer (which may also be referred to as a physical machine or a physical host). Software such as an OS (Operating System) may be executed on each virtual machine. A physical machine which uses virtualization technology executes software for managing a plurality of virtual machines. For example, software referred to as a hypervisor may assign processing ability of a CPU (Central Processing Unit) or memory area of a RAM (Random Access Memory) to a plurality of virtual machines as resources for operation.
In addition, systems including a plurality of physical machines include one capable of switching a physical machine which executes virtual machines thereon. For example, a technique is used which allows migration of data associated with a virtual machine between hypervisors after terminating or without terminating the virtual machine.
For example, when a plurality of virtual machines is to be migrated, there is a proposal to select a set of a virtual machine and a migration method that minimizes the time needed for migration, and create a migration schedule so that the virtual machine selected according to the selected migration method is migrated earlier.
In addition, there is also a proposal to schedule migration of a virtual machine so as to reduce the load on the virtual machine, the physical machine, and the network by grasping or analyzing the variation of the load on the virtual machine, the physical machine, and the network using an approximation formula such as a high-degree equation.
There is also a proposal to restore, when a failure occurs in a backup source system, the backup source system in a restore destination system based on the data preliminarily backed up by the backup apparatus.
Japanese Laid-Open Patent Publication No. 2010-244524
Japanese Laid-Open Patent Publication No. 2010-117760
Japanese Laid-Open Patent Publication No. 2008-243123
It may be desired to migrate a plurality of virtual machines to another physical machine which is different from the current one. That is, for example, when the installation site of the physical machine is affected by a disaster. Migrating virtual machines to a physical machine at another site allows continuation of the processing. However, the time needed to migrate the virtual machines may be limited in the event of an emergency. For example, the building at the site may be about to collapse at the time of a disaster such as an earthquake or a fire. In such a case, it is not always possible for all the virtual machines to migrate to another site within the time limit. Accordingly, there arises a problem of how to efficiently migrate virtual machines.
For example, when any of the virtual machines have failed to be migrated in time, the virtual machines may be restored on a physical machine at another site using preliminarily taken backup data. However, depending on the backup status, sometimes, it is not easy to restore a virtual machine to the state as close as it used to be. For example, the older the backup data is, the more difficult it is to restore to the latest state.